1. Field of Invention
This application concerns the reduction of smoldering tendencies in cellulosic insulation materials, especially in shredded or "loose-fill" form. In particular, the invention relates to methods of treating cellulosic insulation materials with chemicals to render them both sufficiently flame resistant and smolder resistant as to comply with federal safety regulations for such materials.
2. Description of Prior Art
Cellulosic loose-fill insulation has been in use for many years and in recent times has supplied an expanded market for thermal insulation in residential and commercial buildings, and in retrofitting such structures. The chief advantages of loose-fill insulation material are the abundant availability at relatively low cost of raw material such as recycled newspapers and other fibrous cellulosics, the excellent insulating properties of the product, and the ability of the insulation to flow into and fill wall cavities. However, cellulosic loose-fill insulation in untreated form would pose an unacceptable flammability hazard to the structures utilizing such insulation. Accordingly, it is conventional in the loose-fill fiber insulation industry to treat the cellulosic material with combustion retardant compounds such as boric acid, borax, aluminum sulfate and the like prior to use. Representative patent literature in this area includes U.S. Pat. No. 3,027,326 to Moffett which discloses the treatment of insulation materials such as shredded newspaper fluff and shredded wood with a composition consisting of ammonium sulfate, boric acid and potassium alum to reduce the flame and smoldering tendencies of the insulation materials. Other references disclosing the use of phosphates, borates and sulfonates as fire retardants for cellulosic materials include U.S. Pat. No. 2,867,549 to Outterson, U.S. Pat. No. 4,012,507 to Knoepfler and U.S. Pat. No. 4,038,451 to Brown et al. Of all the compositions utilized as combustion retardants for insulation materials, boric acid presently appears to be the most universally used compound, as it is a uniquely effective retardant of smoldering combustion. However, periodic shortages of boric acid and the accompanying price increases of this chemical have been problems in its use and indicate the need for an economical substitute agent for suppressing smoldering.
Accumulating evidence that smoldering ignitions in cellulosic loose-fill insulation were the primary combustion hazard of the material resulted in federal regulations that included provisions to limit smoldering tendencies of the insulation (1978-General Services Administration Specification HH-I-515D, 1979-Consumer Product Safety Commission Interim Safety Standard for Cellulose Insulation). Thus, while the conventional borax, aluminum sulfate and other similar compositions have been widely used as adequate flame retardant compositions for loose-fill insulation materials, all are totally incapable of providing both flame retardancy and acceptable smolder retardant properties. In fact, many of the conventional flame retardant compositions are often used in such quantities and are of such a nature that they actually increase the smolder tendency of the loose-fill insulation material. This is not only true with the insulation industry, but has remained a problem for sometime in the plastics industry. Thus, many attempts have been made at formulating fire retardant compositions for polymeric materials which retard flaming tendencies and, at the same time, inhibit non-flaming combustion or glowing-type combustion as it is sometimes called. A particularly pertinent example of one such attempt is U.S. Pat. No. 3,912,792 to Touval.